Research On Insulation Structure Improvements Of35kV In Service Switchgear Panel

A large number of35kV Switchgear panels are used in the power system.Because the faults of the35kV Switchgear panels directly influence on theelectricity use and their extensive distribution, it is important to keep theSwitchgear panels’ stable operation in order to gauantee the safe and stableoperation of power system. The insulation faults are the most serious problemin the operational investigation reports of SGERPI and Jiangsu power GridCompany. So the insulation faults of35kV Switchgear panels have to beanalysed and the appropriate protection measures need to propose in order toreduce the potential hazard of them during the power system operation.This paper investigates and analyses the insulation faults of35kV inservice cable outgoing switchgear panels (KYN-40.5type) in Qidong powerSupply Company. The conculsion of this investigation and analysis is themain reason of insulation faults attribute to the irrational layout of switchgearpanels insulation structure and the humid environments effect. Theovervoltage risk of real35kV overhead line and substation (including35kVcable outgoing Switchgear panels) are conculated and analysed. Because thelow insulation level, the arc ground overvoltage caused by single groundingfault and the invading wave overvoltage caused by backflashover andlightning induced overvoltage are the most severe overvoltage risk the35kVcable outgoing Switchgear panels faced with. It is important to take measuresto linit these overvoltages. Then, this paper proposes three type ofmeasurements to improve the insulation sutructure of the35kV cableoutgoing Switchgear panel (KYN-40.5type). There are adjustment ofinsulation sutructure inside the Switchgear panel, the use of new insulationmaterial and technics, and the increasement of Switchgear panel’s dehumidification ability. The drawing is designed and the improvements ofSwitchgear panel is fabricated and installed. The two Switchgear panels(before and after improvements) are compared through experimental method(such as power frequency, lightning impulse, insulation resistancemeasurements and humid emvionments simulation) under different condition.The experiment results show the insulation of improved Switchgear panel isgreatly enhanced and could be safe in operation under overvoltage and humidemvionment condition. In addition, the improved Switchgear panels are stillunder safe operation after place in service. The conclusion of this paper couldbe used to provide a reference for the same type of35kV in serviceSwitchgear panel.